离心泵非设计工况内部流动特性研究

Study on the Internal Flow Characteristics of a Centrifugal Pump Under Off-design Conditions

以单级蜗壳式离心泵为研究对象,基于RANS进行了全流场的非定常数值计算,探讨了叶轮的非定常流动特征,重点分析了叶轮出口沿轴向变化的圆周面流域内各节点的压力分布特性。结果表明:在叶片压力面及叶片后缘尾迹区发生了剧烈的湍流脉动现象;不同工况下叶轮出口圆周方向的压力系数C_p均在隔舌附近产生极值;额定工况Q/Q_N=1时,叶轮出口圆周方向的压力系数C_p呈稳定周期性分布,随着工况的改变,压力系数C_p沿蜗壳周向分布不均匀性增加;小流量工况下叶轮流域内发生了明显的流动分离现象,流道内产生了较大尺度的分离涡,破坏了叶轮出口圆周方向压力系数C_p的周期性分布特性;叶轮出口圆周压力系数C_p沿中截面两侧的流域内几乎对称分布;在Q/Q_N=0.2小流量工况下,压力脉动频谱图低频段内出现了较多复杂的激励信号,认为这与流域内的分离涡结构具有一定关联。

Set the single stage volute centrifugal pump as research object meanwhile based on the RANS to simulate the unsteady flow characteristics of the whole flow field,and then researched on the unsteady flow characteristics of the impeller,which focused on the pressure distribution and fluctuation characteristics of each node along the axial direction that changes in circumference field of impeller outlet.The results shows that the phenomenon of intense turbulence pulsation happened in the pressure surface and the trailing edge of the blade.The pressure coefficient Cp in the circumferential direction of the impeller outlet reached to the extreme value around the tongue under different conditions.The pressure coefficient Cp in the circumferential direction of the impeller outlet has a stable periodic distribution under the rated condition,the non-uniformity of the pressure coefficient Cp along the circumferential direction increases while the working condition changed.The flow separation phenomenon occurred obviously under small flow rate condition and appeared large scale separation vortex which destroyed the periodic distribution of the impeller outlet pressure coefficient Cp along the circumferential direction.Complicated exciting signals were found in the pressure pulsation frequency graph at small flow rate condition,which may related to the vortex structure in the pump.